With reference to FIG. 1, a motion transmission system in a bicycle 1100 comprises a chain 1101 extending between toothed wheels 1102, 1103 associated with the axle of the pedal cranks 1104 and with the hub 1105 of the rear wheel 1106. When—as in the case shown—at at least one of the axle of the pedal cranks 1104 and the hub 1105 of the rear wheel 1106 there is a group of toothed wheels 1102, 1103 comprising more than one toothed wheel 1102, 1103, and the motion transmission system is therefore provided with a gearshift 1110, a front derailleur 1111 and/or a rear derailleur 1112 are provided for.
In the case of an electronic gearshift, control electronics change the gear ratio automatically, for example based on one or more detected variables such as the travel speed, the cadence of rotation of the pedal cranks, the torque applied to the pedal cranks, the slope of the travel terrain, the heart rate of the cyclist and similar, and/or the gear ratio is changed based on commands manually input by the cyclist through suitable control members, for example levers and/or buttons, typically provided on one or two manual control devices 1107 mounted on the handlebars 1108 of the bicycle 1100.
In the case of a mechanical gearshift, the gear ratio is changed based on commands manually input by the cyclist through suitable control members, typically levers, typically provided on the manual control devices 1107 mounted on the handlebars 1108 of the bicycle 1100.
Each derailleur 1111, 1112 includes a support body 1113, 1114 that is configured to be attached to or mounted on the frame 1109 of the bicycle 1100, and a movable body 1115, 1116 comprising a chain guide 1117, 1118 movable to displace the chain 1101 among the toothed wheels 1102, 1103 in order to change the gear ratio. The chain guide 1117, 1118 is also called cage in the case of a front derailleur, and rocker arm in the case of a rear derailleur.
In the case of an electronic gearshift, the movable body 1115, 1116 comprising the chain guide 1117, 1118 is moved through an electromechanical actuator. Each electromechanical actuator in turn typically comprises a motor, typically an electric motor, coupled with the movable body through a linkage. Typically, the electric motor is provided with a gear reduction mechanism. The assembly of electric motor and gear reduction mechanism is referred to hereinafter as geared motor. The actuator typically further comprises a sensor or transducer of the position, speed, acceleration and/or direction of rotation, of the rotor of the motor or of any movable part downstream of the rotor, down to the chain guide 1117, 1118 itself. It is worth emphasizing that slightly different terminology from that used in this context is also in use.
In the case of a mechanical gearshift, the movable body 1115, 1116 comprising the chain guide 1117, 1118 is moved through an analogous linkage controlled by the traction and release of an inextensible, usually sheathed cable (Bowden cable); in the manual control device 1107 a mechanism for controlling the traction of the cable is provided, typically comprising a cable-winding bush and an indexer to determine the rotation and the stopping of the cable-winding bush in predetermined positions—“indexed bush” or “bush-indexer assembly”—as well as one or more manual actuation members, typically of the lever type, to control the bush-indexer assembly.
In the case of a rear derailleur 1112, the linkage typically comprises two connecting rods, the ends of which are articulated to the support body 1114 and to the movable body 1116 to form an articulated parallelogram. The geared motor, the Bowden cable respectively, drives the articulated parallelogram open and close, and consequently controls the displacement of the chain guide 1118 among the toothed wheels 1103.
In some known electronic gearshifts a central battery power supply unit is provided, shared by all of the components of the gearshift 1110, and typically arranged in a rather central position on the bicycle frame 1109. U.S. Pat. No. 9,005,059 B2 describes a rear derailleur wherein the motor is electrically connected to a remote battery power supply unit.
In other electronic gearshifts, a battery power supply unit dedicated to the rear derailleur 1112 (besides one or more other battery power supply unit/s dedicated to the other components of the gearshift) is provided. In such cases, the battery power supply unit is typically supported on the bicycle frame 1109 close to the support body 1114 of the rear derailleur 1112, like for example in U.S. Pat. No. 8,979,683 B2 or in EP 2 727 810 A2. DE 10 2016 001 333 A1 discloses a battery power supply unit a support bracket of which is mounted on the frame with a same fixing device as the derailleur.
Furthermore, the battery power supply unit can be supported on the support body 1114 itself of the rear derailleur 1112—examples of such a derailleur can be found in EP 2 865 589 A1, US 2016/0221640 A1, as well as in EP 2 722 266 B1, EP 1 752 373 B1, which in particular disclose a front derailleur.
Indeed, it has always been believed, in the field of bicycle components, that the linkage of the derailleur should move an as light as possible load, so as not to require particularly great sizing and strength and, in the case of an electronic gearshift, so as to be able to exploit an as small as possible electric motor and with as low as possible electrical power consumption in order to allow the maximum possible autonomy away from the electrical network.
Moreover, EP 2 712 799 B1 discloses a rear derailleur wherein the battery power supply unit is connected to one of the support body and the movable body, the motor being placed on the other one.
Italian patent application no. 102016000069087, still secret at the date of first filing of the present patent application, discloses a bicycle front electric derailleur comprising a support body that is configured to be attached to a bicycle frame, a chain guide connected to the support body through a linkage, an electric motor that controls the linkage to displace the chain guide among toothed wheels of a motion transmission system, and a battery power supply unit, characterized in that the battery power supply unit is supported by the chain guide.